From affd474311fe9cb4dbbcb958742b73cb27037ffb Mon Sep 17 00:00:00 2001
From: Dmitriy Nesteryuk <dmitriy.nesteryuk@gmail.com>
Date: Tue, 27 Oct 2020 08:48:00 +0200
Subject: [PATCH] fix a performance issue with dependent params
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Fixes https://github.com/ruby-grape/grape/issues/2100

The reason was in `ActiveSupport::HashWithIndifferentAccess`, it
is super expensive.

When users use a `Grape::Extensions::ActiveSupport::HashWithIndifferentAccess::ParamBuilder`
or `Grape::Extensions::Hashie::Mash::ParamBuilder` parameter builder
there is no change. However, users who use `Grape::Extensions::Hash::ParamBuilder`
must make sure a parameter to be dependent on must be a symbol.

    given :matrix do
      # block here
    end

Benchmark after this fix:

Warming up --------------------------------------
               Given     1.000  i/100ms
              Simple     1.000  i/100ms
Calculating -------------------------------------
               Given      0.804  (± 0.0%) i/s -     49.000  in  61.186831s
              Simple      0.855  (± 0.0%) i/s -     52.000  in  60.926097s

Comparison:
              Simple:        0.9 i/s
               Given:        0.8 i/s - 1.06x  slower
---
 CHANGELOG.md                          |  1 +
 UPGRADING.md                          | 22 ++++++++++++++++++++++
 lib/grape/validations/params_scope.rb |  5 +++--
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 75f599fb33..4aefdb27d6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#2127](https://github.com/ruby-grape/grape/pull/2127): Fix a performance issue with dependent params - [@dnesteryuk](https://github.com/dnesteryuk).
 * [#2126](https://github.com/ruby-grape/grape/pull/2126): Fix warnings about redefined attribute accessors in `AttributeTranslator` - [@samsonjs](https://github.com/samsonjs).
 * [#2121](https://github.com/ruby-grape/grape/pull/2121): Fix 2.7 deprecation warning in validator_factory - [@Legogris](https://github.com/Legogris).
 * [#2115](https://github.com/ruby-grape/grape/pull/2115): Fix declared_params regression with multiple allowed types - [@stanhu](https://github.com/stanhu).
diff --git a/UPGRADING.md b/UPGRADING.md
index 9d63392b96..e5b6947fa2 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -1,6 +1,28 @@
 Upgrading Grape
 ===============
 
+### Upgrading to >= 1.5.1
+
+#### Dependent params
+
+If you use [dependent params](https://github.com/ruby-grape/grape#dependent-parameters) with
+`Grape::Extensions::Hash::ParamBuilder`, make sure a parameter to be dependent on is set as a Symbol.
+If a String is given, a parameter that other parameters depend on won't be found even if it is present.
+
+_Correct_:
+```ruby
+given :matrix do
+  # dependent params
+end
+```
+
+_Wrong_:
+```ruby
+given 'matrix' do
+  # dependent params
+end
+```
+
 ### Upgrading to >= 1.5.0
 
 Prior to 1.3.3, the `declared` helper would always return the complete params structure if `include_missing=true` was set. In 1.3.3 a regression was introduced such that a missing Hash with or without nested parameters would always resolve to `{}`.
diff --git a/lib/grape/validations/params_scope.rb b/lib/grape/validations/params_scope.rb
index a51be6e1e1..792762b06a 100644
--- a/lib/grape/validations/params_scope.rb
+++ b/lib/grape/validations/params_scope.rb
@@ -61,8 +61,9 @@ def meets_dependency?(params, request_params)
         end
 
         return params.any? { |param| meets_dependency?(param, request_params) } if params.is_a?(Array)
-        return false unless params.respond_to?(:with_indifferent_access)
-        params = params.with_indifferent_access
+
+        # params might be anything what looks like a hash, so it must implement a `key?` method
+        return false unless params.respond_to?(:key?)
 
         @dependent_on.each do |dependency|
           if dependency.is_a?(Hash)